The markets today celebrated as if Ireland had signed on the dotted line and thereby somehow prevented the spread of contagion within the eurozone. There are two reasons why this outbreak of optimism looks premature. The first is that Ireland has not yet agreed to anything. Yes, it has accepted that some form of bailout – or a massive loan that is "shown but not used", as central bank governor Patrick Honohan put it – is inevitable. But there's a lot of haggling left in these negotiations.

The German and French governments are determined to seize the moment to instruct Ireland to lift its rate of corporation tax, currently set at 12.5%, which has attracted the likes of Pfizer to the country. Yet whacking up corporate taxes and risking an exit of multinationals, would clearly be terrible for the Irish economy and its banking system. In this standoff, the Irish government's best weapon is procrastination: it needs to make Angela Merkel fear that she might make the eurozone's problems worse by insisting on a tax rise.

Then there is the huge question of Irish banks' continued access to the European Central Bank's liquidity facilities. The ECB and Germany resent Ireland's reliance on such support, which is partly why this crisis has blown up now. But how quickly will Irish banks be asked to wean themselves off cheap financing from Frankfurt?

In theory, making the Irish government accept a huge loan in order to shove more capital into its banks would make the institutions more able to finance themselves. In practice, there's no guarantee this would happen – and if it doesn't the ECB can hardly step away from the Irish banks. Greek banks are still allowed to tap the ECB merrily.

The second unsafe assumption is that shoring up Ireland's banks automatically improves the position of Portugal. The bond markets determine the price at which Portugal can fund its budget deficit. Recent experience suggests that, once Ireland has suffered its turn in the spotlight, the show will roll on to the next weak link. Indeed, by accelerating the confrontation in Ireland, the eurozone big boys may merely ensure that battles elsewhere are fought sooner rather than later.